eal/linux: fix numa node detection

Using the "physical_package_id" as a fallback for determining the
numa node of a core tends to be unreliable. Fix this by using a
detection routine which reads the numa information from
/sys/devices/system/node and just returns a numa node of 0 on
failure.

Reported-by: Wang Sheng-Hui <shhuiw@gmail.com>
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Stephen Hemminger <stephen@networkplumber.org>

diff --git a/lib/librte_eal/linuxapp/eal/eal_lcore.c b/lib/librte_eal/linuxapp/eal/eal_lcore.c
index ef8c433..560039b 100644 (file)
--- a/lib/librte_eal/linuxapp/eal/eal_lcore.c
+++ b/lib/librte_eal/linuxapp/eal/eal_lcore.c
@@ -49,7 +49,7 @@
 
 #define SYS_CPU_DIR "/sys/devices/system/cpu/cpu%u"
 #define CORE_ID_FILE "topology/core_id"
-#define PHYS_PKG_FILE "topology/physical_package_id"
+#define NUMA_NODE_PATH "/sys/devices/system/node"
 
 /* Check if a cpu is present by the presence of the cpu information for it */
 static int
@@ -66,58 +66,26 @@ cpu_detected(unsigned lcore_id)
        return 1;
 }
 
-/* Get CPU socket id (NUMA node) by reading directory
- * /sys/devices/system/cpu/cpuX looking for symlink "nodeY"
- * which gives the NUMA topology information.
- * Note: physical package id != NUMA node, but we use it as a
- * fallback for kernels which don't create a nodeY link
+/*
+ * Get CPU socket id (NUMA node) for a logical core.
+ *
+ * This searches each nodeX directories in /sys for the symlink for the given
+ * lcore_id and returns the numa node where the lcore is found. If lcore is not
+ * found on any numa node, returns zero.
  */
 unsigned
 eal_cpu_socket_id(unsigned lcore_id)
 {
-       const char node_prefix[] = "node";
-       const size_t prefix_len = sizeof(node_prefix) - 1;
-       char path[PATH_MAX];
-       DIR *d = NULL;
-       unsigned long id = 0;
-       struct dirent *e;
-       char *endptr = NULL;
-
-       int len = snprintf(path, sizeof(path),
-                              SYS_CPU_DIR, lcore_id);
-       if (len <= 0 || (unsigned)len >= sizeof(path))
-               goto err;
+       unsigned socket;
 
-       d = opendir(path);
-       if (!d)
-               goto err;
+       for (socket = 0; socket < RTE_MAX_NUMA_NODES; socket++) {
+               char path[PATH_MAX];
 
-       while ((e = readdir(d)) != NULL) {
-               if (strncmp(e->d_name, node_prefix, prefix_len) == 0) {
-                       id = strtoul(e->d_name+prefix_len, &endptr, 0);
-                       break;
-               }
-       }
-       if (endptr == NULL || *endptr!='\0' || endptr == e->d_name+prefix_len) {
-               RTE_LOG(WARNING, EAL, "Cannot read numa node link "
-                               "for lcore %u - using physical package id instead\n",
-                               lcore_id);
-
-               len = snprintf(path, sizeof(path), SYS_CPU_DIR "/%s",
-                               lcore_id, PHYS_PKG_FILE);
-               if (len <= 0 || (unsigned)len >= sizeof(path))
-                       goto err;
-               if (eal_parse_sysfs_value(path, &id) != 0)
-                       goto err;
+               snprintf(path, sizeof(path), "%s/node%u/cpu%u", NUMA_NODE_PATH,
+                               socket, lcore_id);
+               if (access(path, F_OK) == 0)
+                       return socket;
        }
-       closedir(d);
-       return (unsigned)id;
-
-err:
-       if (d)
-               closedir(d);
-       RTE_LOG(ERR, EAL, "Error getting NUMA socket information from %s "
-                       "for lcore %u - assuming NUMA socket 0\n", SYS_CPU_DIR, lcore_id);
        return 0;
 }